Secure radio communication systems that employ encryption are known in the art. Such systems utilize encryption keys to ensure that only communication units with valid encryption keys can communicate securely.
Encryption keys, commonly known as keys, in a secure communication system are managed by a key management controller (KMC). The KMC can assign keys to communication units. Typically, a key is assigned by over-the-air-rekeying (OTAR), whereby the KMC provides the key to a communication unit over a radio channel. Alternatively, the key can be provided by temporarily connecting the communication unit to a key-variable-loader (KVL). OTAR and the KVL allow the KMC to change key assignments of communication units when desired.
Typically, a communication unit that operates at a home location is affiliated with a local KMC. When the communication unit roams to a remote location, the KMC at the remote location determines that the communication unit is not affiliated but can provide the communication unit with a key.
Presently, providing the key to the roaming communication unit requires: prior knowledge of the destination; loading the roaming communication unit with a unique shadow key provided by the local KMC; including the roaming communication unit in the database of the destination KMC by communications between the operators at the local KMC and the destination KMC; and upon arrival at the destination, loading the roaming communication unit with the key.
With increasing mobility of staff between national and international locations, a need has developed for a better method of providing keys to roaming communication units.